SAN DIEGO (CBS 8) – The waters off Mission Beach are closed for the second time in 24 hours, after a second shark sighting Friday morning.

An experienced surfer spotted a 14-inch dorsal fin in the water near Tower 13 at about 8:00 a.m.

People were pulled out of a two-mile stretch of water off Mission Beach, which is roughly the same area that was closed Thursday after a lifeguard said he saw a great white with an 18-inch dorsal fin. That sighting was located at Tower 15.

This is a breaking news alert. Previous stories on Thursday's sighting are below.

SAN DIEGO (CNS) - A two-mile stretch of water off Mission Beach reopened Friday after a shark scare prompted a closure of the area, lifeguards said.

The area was closed about 12:30 p.m. Thursday after an 18-inch dorsal fin was spotted near tower 15, lifeguards said. The size of the fin indicated it could belong to a shark at least 10 feet long.

Lifeguards closed the waters one mile in each direction from the location of the sighting, according to Lt. Nick Lerma.

Lifeguards searched the ocean with the help of a San Diego Fire-Rescue helicopter but no other sightings were reported, lifeguards said.

This is an update to the previous story below.

SAN DIEGO (CNS) - Lifeguards closed a two-mile stretch of water off Mission Beach after spotting an 18-inch dorsal fin Thursday.

The dorsal fin was seen around 12:30 p.m. near Tower 15, prompting lifeguards to close the waters one mile in each direction, Lt. Nick Lerma said.

Lerma said the size of the fin indicates that it could belong to a shark that is at least 10 feet long.

Lifeguards searched the ocean with the help of a San Diego Fire-Rescue helicopter but no other sightings were reported, Lerma said.

The area will remain closed for the rest of Thursday but will be open Friday morning, he said.